1. Field of the Invention
This invention relates to apparatus for controlling the discharge temperature of a common thermal source providing thermal fluid to one or more HVAC systems in a network, and more particularly to electronic processing apparatus for controlling the common thermal source such as to modulate the discharge temperature of the thermal fluid in dependence on the HVAC system having the highest thermal energy demand.
2. Description of the Prior Art
As may be known, HVAC systems are used for controlling the environmental temperature conditions in one or a plurality of structurally enclosed living spaces associated with each system. The HVAC systems may be of a variety of well known types, such as multi-zone, dual duct, or terminal reheat type systems. In general, such HVAC systems include separate sources of heating and cooling within the system, however, they may include either heating or cooling apparatus alone. In large facilities, such as multi-storied office buildings, schools, or a facility comprising a complex of some number of individual buildings, a plurality of HVAC systems are used for controlling different segments of the facility, i.e. separate floors, or groups of floors in a multi-storied building, or separate buildings in a complex. In general, the plurality of HVAC systems in a single facility are connected in a network which is serviced by a common thermal source, which may include either, or both of a separate cold source and hot source, and which provides the thermal energy required by the heating and/or cooling apparatus of the individual HVAC systems of the network. As may be known, in the prior art HVAC networks each of the HVAC systems operates autonomously in responding to, and providing for the temperature regulation in the living spaces associated with that system. As such, each HVAC has separate thermal energy demands in dependence on the summation of the energy demands from all of the system spaces. In general, the prior art control systems for the common thermal source provide regulation of the souce discharge temperature at a set point temperature value which is preset for a given time period, i.e. a heating or cooling season, or possibly on a monthly or weekly interval to ensure a discharge temperature in satisfaction of the total demand from all of the HVAC systems in the network. The common source set point temperature may be changed by a maintenance operator at the source site in anticipation of the change in total network demand resulting from changed ambient environmental conditions, however, due to the location of the individual HVAC systems in the network at various site locations which may be relatively remote from each other and from the location of the common source adjusting the discharge temperature set point as necessary to satisfy the short term energy demands of the network has been impractical, if not impossible due to the inability to accurately determine the short term thermal energy demand of the individual HVACs in the system. Therefore, the prior art systems control the discharge temperature to the anticipated worst case condition to ensure the comfort of the occupants of the various living spaces. As may be appreciated, the result is wasteful energy consumption in favor of ensuring adequate system performance.